1. Field of the invention
This invention relates to a rotary roller pump for carrying out a sequential pumping of fluid in a plurality of separate squeezable tubings.
Although the rotary roller pump according to this invention can be advantageously used in technological applications in general, wherein it is desired to perform, by means of only one pump, sequential pumping operations on two or more separate tubings, this invention will be described by making specific reference to its applicatons in the medical field and particularly in the establishment of extra-corporeal blood circulation which is made necessary for instance during the dialysis and ultrafiltration of blood, and within the frame of various medical and surgical interventions and situations which require the use of the so-called "heart-lung machines" and similar devices.
2. Description of the prior art
Within the frame of the above mentioned medical and surgical situations, there is a frequent need to have at one's disposal some devices by means of which an alternate pumping on the hematic liquid conveyed along two separate and distinct tubings is accomplished (pumps for use in the boimedical field are e.g. disclosed in the U.S. Pat. Nos. 2,659,368; 2,705,493; and 3,045,601). For instance, when performing the dialysis and ultrafiltration of blood with the cannulation technique with a single needle and a Y-junction, in the extra-corporeal circuit which comprises a length of arterial line for transferring the blood to be purified from the patient's arterialised vein to the dialyzer, and a length of venous line for conveying the purified blood from the dialyzer to the arterialised vein, a double-pumping action is needed to ensure the required blood flow rate. Because the pumping operations on the arterial and venous lines of the circuit must alternate according to a preset time sequence, the use of two pumps or a double-head pump not only requires distinct driving means but also electronic synchronizing means for actuating the pumps or the pump heads according to the pre-established time sequence. This in turn does not only increase the complexity of the pumping devices with the attendant increase of the risk that breakdowns and interruptions may take place, but also weighs heavily on the manufacturing and maintenance costs of the units in which the above mentioned extra-corporeal circuits are used.